28o 



BULLETIN OF THE BUREAU OF FISHERIES. 



Tabulations of Propagative Structures in Potamogeton crispus, June i6, igij^Continued. 



(B) SEED FORMATION. 



Table A shows a preponderance of burs over floral spikes; table B, a preponderance 

 of sterile spikes over fertile ones. A comparison of the tables A and B shows that bur 

 formation exceeds seed production; that is, the important mode of increase is by vegeta- 

 tive means. It should be remembered in this connection, however, that the bur which 

 is the most conspicuous is but one of several vegetative structures contributing to the 

 rapid extension of this species, and that seed production is, therefore, even less important 

 relatively than the tables suggest it to be. 



Tabulation of Propagative Structures in Potamogeton pectinatus, September 30, 1913. 



o Imperfect record. 



'* This plant bore one sterile spike. 



The fertile spikes of P. pectinatus produce, in general, from 10 to 15 seeds. The 

 tubers occur singly, in pairs, and in threes. Bearing these possibilities in mind, the 

 tabulation of P. pectinatus indicates a close approximation to equality in the produc- 

 tion of seeds and tubers. The small number of plants from which the data were collected 

 is an objection which could be justly put forward, yet the results conform in general 

 with field observations in restricted areas where the common form of pectinatus 



